Brandi McGrath noticed fewer campers last weekend at Yosemite Ridge Resort, but it wasn’t because of reports of plague in the adjacent national park.

It’s because the school year started.

McGrath, who owns the private campground in Groveland, California with her husband Joe, said they had a handful of campers come to Yosemite Ridge after their reservations inside the park were cancelled due to the cases of plague.

Even with the transferred campers, nothing out of the ordinary occurred.

“Everything has been normal,” McGrath told Healthline. “We’re pretty booked up.”

Several campgrounds outside of Yosemite contacted by Healthline said they had no reservation cancellations because of concerns of the plague.

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Plague Cases Near Yosemite Investigated

The California Department of Public Health is investigating a second case of the plague in people vacationing in Yosemite National Park, the Sierra National Forest, and surrounding areas.

The latest case involves a tourist from Georgia. The initial case, reported August 6, involved a child from Los Angeles County.

The plague had been confirmed in the areas of the Crane Flat Campground, the closest camping site to the popular Yosemite Valley that isn’t in the valley itself. The other was in Tuolumne Meadows, another campground 38 miles northeast of Crane Flat.

The National Parks Service closed Crane Flat for four days while workers with the state public health department sprayed the area for fleas, concentrating on burrows of rodents that could be potential carriers of the plague.

Crane Flat was schedule to open today.

Dr. Karen Smith, state public health director, said the closure was done with an abundance of caution. While threats to humans are low, government agencies have been warning recent visitors of the park to consider plague as a cause of their symptoms, should they become sick.

“Warnings issued in California regarding plague were useful all the way across the country in Georgia,” she said in a press release. “Those warnings helped the patient get the prompt medical attention necessary to recover from this illness.”

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Plague Still Lingers in Western United States

The western United States is a hotbed of tourist activity, from the warm climates in the winter to the natural splendor found in parks like Yosemite.

Drought, famine, and disease didn’t stop earlier settlers and it doesn’t seem to have much of an effect on weekend warriors.

Only one person called Yosemite Ridge with concerns about the plague and no one called with such concerns to the nearby Yosemite Pines Campground, according to their owners.

Campers, McGrath said, were more concerned about the potential ill effects of California’s continuing drought.

“I had more people concerned about falling limbs and fires than the plague,” she said.

While the reports of human infections at Yosemite are new — the last confirmed case occurring in 1959 — the plague is endemic to the western United States.

Since the plague was first introduced into the United States via trade ship in 1900, there have been 1,006 cases.

While the fleas came from rats aboard the ship, they soon spread to other rodents, such as mice, squirrels, chipmunks, and prairie dogs, all who call Yosemite and other parts of the western United States home.

In California, plague-infected animals are most often found in the mountains, the foothills, and sometimes along the Pacific coast.

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How the Plague Affected History and Humans Today

The plague is spread from ticks infected with the bacteria Yersinia pestis.

While their bites spread the illness, they do not require a host, so they can transfer from animals to humans. That also means that they can remain behind on dead animals.

Investigators are still attempting to determine how the two Yosemite visitors came in contact with the fleas.

Early symptoms of plague can include fever, chills, nausea, weakness, and swollen lymph nodes in the neck, armpit, or groin. When the plague infects the lymph nodes, it’s known as the bubonic plague.

If left untreated, the plague is deadly, as history has shown many times over.

In the mid-1300s, the “Black Death” spread along the world’s most popular trade routes, killing as much as a third of Europe’s population.

Now, cases of the plague are only commonly found in sub-Saharan Africa and Madagascar, which constitute 95 percent of the world’s plague cases, according to the U.S. Centers for Disease and Control and Prevention (CDC).

The United States sees an average of seven cases of plague a year, the CDC states.

Modern day antibiotics are sufficient to wipe out an infection, and incidents of the plague often occur in rural areas where the fewest humans are affected.

When cases are reported, patients are treated and suspected infection areas are treated with pesticides to cut down the flea population.

“By eliminating the fleas, we reduce the risk of human exposure and break the cycle of plague in rodents at the sites,” Smith said. “People can protect themselves from infection by avoiding any contact with wild rodents.”

How to Avoid the Plague Like the Plague

The California public health department says that there are some precautionary steps people can take to reduce their risk of coming into contact with fleas carrying the plague:

  • Never feed squirrels, chipmunks or other rodents.
  • Never touch sick or dead rodents.
  • Avoid rodent burrows.
  • Wear long pants tucked into socks or boot tops to reduce exposure to fleas.
  • Spray insect repellent containing DEET on socks and pant cuffs to reduce exposure to fleas.
  • Keep wild rodents out of homes, trailers, and outbuildings, and away from pets.